(a) Field of the Invention
The present invention relates to an electrolyte for lithium secondary batteries containing a chelating agent, and a lithium secondary battery comprising said electrolyte.
(b) Description of the Related Art
Recently, the compact and lightweight construction of electronic equipment has been realized and the use of portable electronic devices has been generalized, and thus studies on secondary batteries having high energy density have been actively conducted.
Lithium secondary batteries, which are currently mainly used, comprise cathode and anode made of materials capable of intercalating and deintercalating lithium ions, are fabricated by injecting a non-aqueous electrolyte between the cathode and anode, and produce electrical energy by oxidation and reduction reactions, which occur when lithium ions are intercalated into and deintercalated from the cathode and anode.
When the secondary battery is charged and discharged, transition metal ions in the battery can cause side reactions and can result in a reduction in the performance of the battery. For example, when the cathode contains Fe impurities, Fe can be ionized, and deposited on the anode, resulting in voltage drop. Also, some Co, which is used as the cathode active material, can be dissolved out and deposited on the anode, and when spinel Mn is used for the cathode, Mn can be dissolved. In addition, when a Fe olivine material is used, Fe can be dissolved out. Such side reactions deteriorate the stability and performance of the battery.
In a prior attempt to suppress side reactions, an expensive apparatus for purifying raw materials is used, the pretreatment of raw materials is performed, or other alternative materials having poor performance are used. However, such methods have problems in that they are expensive and deteriorate the performance of the battery.